Internal combustion engines are supplied with a mixture of air and fuel for combustion within the engine that generates mechanical power. To maximize the power generated by this combustion process, the engine is often equipped with a turbocharged air induction system. A turbocharged air induction system includes a turbocharger that uses exhaust from the engine to compress air flowing into the engine, thereby forcing more air into a combustion chamber of the engine than the engine could otherwise draw into the combustion chamber. This increased supply of air allows for increased fueling, resulting in an increased engine power output.
A turbocharger generally comprises a compressor wheel mounted on one end of a single shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing. A bearing housing is connected between the turbine and compressor housings for containing bearings for the shaft. The turbine housing receives exhaust gas from the engine and directs it to the turbine wheel which is driven by the exhaust gas. The turbine assembly thus extracts power from the exhaust gas and drives the compressor.
The connection between the compressor wheel and the turbocharger shaft typically involves the turbocharger shaft being received in an internal bore in a boss that extends from the hub of the compressor wheel. However, such connections can lose radial piloting during operation of the turbocharger which can lead to shaft imbalance. Piloting the hub of the compressor wheel inside of a shaft can lead to high stresses as the impeller grows into the interface during operation of the turbocharger.